Question
Why can due date estimates differ?
Different methods start from different assumptions, and real pregnancies do not all follow exactly the same timeline. This tool is best used as a planning estimate, not a diagnosis.
Fitness
Use OmniCalc's due date calculator to estimate your due date and pregnancy timing milestones from a few common starting points.
Due date calculator
Use a last menstrual period, conception date, or IVF timing reference to estimate due date, gestational age, and trimester milestone timing.
Why this result matters
A pregnancy timing estimator focused on due date, gestational age, and trimester milestones using LMP, conception date, or IVF transfer timing. Use the tool above to enter a few clear inputs and get a practical answer you can use right away.
This due date calculator estimates an expected due date from last menstrual period, conception date, or IVF transfer timing. It also shows gestational age, estimated conception timing, and major trimester milestones so users can turn a date estimate into a more practical planning view.
Formula and method
The calculator adds a standard pregnancy-duration offset to the selected starting date: LMP + 280 days, conception + 266 days, IVF day-3 + 263 days, or IVF day-5 + 261 days, then estimates gestational age and trimester timing from that baseline.
Example
If someone knows their last menstrual period or conception date, the calculator estimates an expected due date and shows how far along the pregnancy may be as of a selected date.
FAQ
Short answers to the questions people often ask before or after using the tool.
Question
Different methods start from different assumptions, and real pregnancies do not all follow exactly the same timeline. This tool is best used as a planning estimate, not a diagnosis.
Question
You can switch the method to conception date so the estimate uses the shorter 266-day interval from conception rather than the usual 280-day interval from LMP.
Question
No. It is a simple planning tool and should not replace a clinician's guidance or ultrasound-based dating.
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